The present invention relates to systems for removal of odors emitted from animal and food production environments and, more particularly, to ozone and non-thermal plasma reactors for decomposing odorous compounds.
Industries have devoted considerable effort to develop a variety of technologies to reduce odorous emissions from animal and food production facilities. However, these technologies are typically ineffective or too expensive to implement. For example, ozones have been used to remove larger, more unstable compounds from odorous gas emissions. While ozone generators are fairly energy efficient, these types of generators are not effective in removing smaller, more stable odorous compounds such as ammonia and hydrogen sulfide. Alternatively, plasma has been proposed as a means for removing odorous compounds. Plasma is regarded as the fourth state of matter (ionized state of matter). Unlike thermal plasmas, non-thermal plasmas (NTPs) are in gaseous media at near-ambient temperature and pressure out have electron mean energies considerably higher than other gaseous species in the ambient environment. NTP species include electrically neutral gas moleculest charges particles in the form of positive ions, negative ions, free radicals and electrons, and quanta of electromagnetic radiation (photons). These NTP species are highly reactive and can convert odorous compounds to non-odorous compounds or less-odorous compounds through various chemical reaction mechanisms. In contrast to thermal processes (such as thermal plasma), an NTP process directs electrical energy to induce favorable gas chemical reactions, rather than using the energy to heat the gas. Therefore, NTP is much more energy- efficient than thermal plasma.
NTPs can be generated by electric discharge in the gas for injection of electrons into the gas by an electron beam. Electron beams must be accelerated under a high vacuum and then transferred through special windows to the reaction site. The reaction site must be sized with respect to the penetration depth of the electrons It is much more difficult to scale-up the size of an electron beam reactor than electric discharge reactors. Therefore, electron beam reactors are less favored than electric discharge reactors.
Among the various types of electric discharge reactors, pulse corona and dielectric barrier (silent) discharge reactors are very popular for their effectiveness and efficiency. However, pulse corona reactors have the major disadvantage of requiring special pulsed power supplies to initiate the pulse corona. Consequently, dielectric barrier discharge has become a fast growing technology for pollution control.
Cylindrical and planar reactors are two common dielectrical barrier discharge reactor configurations. Both of these configurations are characterized by the presence of one or more insulating layers in a current path between two metal electrodes, in addition to the discharge space. Other dielectric barrier discharge reactors include packed-bed discharge reactors, and surface discharge reactors.
There are several major difficulties in the practical use of dielectric barrier discharge reactors for odorous gas removal. These difficulties include an expensive power supply, low energy efficiency and flow rate, and the blocking of discharge volume by dusts in the feed gas and/or solid mineral compounds produced during the plasma reactions. More effective and economical barrier discharge reactors are desired.
On aspect of the present invention relates to an odor removal system, which includes an odorous gas inlet, a treated gas outlet and a gas treatment flow path from the odorous gas inlet to the treated gas outlet. A mixer is coupled in series with the gas treatment flow path and has an ozone inlet coupled to an ozone outlet of an ozone generator. A non-thermal plasma reactor is also coupled in series with the gas treatment flow path.
Another aspect of the present invention relates to a non-thermal plasma discharge reactor, which has an inlet and an outlet. A reaction volume is coupled between the inlet and the outlet. A generally planar ground electrode is positioned along one side of the reaction volume and has a plurality of surface non-uniformities adapted to generate a non-uniform plasma within the reaction volume. A generally planar high-voltage electrode is positioned along an opposite side of the reaction volume with respect to the ground electrode and is separated from the reaction volume by a dielectric barrier.
Another aspect of the present invention relates to a non-thermal plasma discharge reactor having an inlet and an outlet. The reaction volume is coupled between the inlet and the outlet. A generally planar ground electrode is positioned along one side of the reaction volume and extends beyond the reaction volume to form a cooling fin external to the reaction volume. A generally planar high-voltage electrode is positioned along an opposite side of the reaction volume with respect to the ground electrode and is separated from the reaction volume by a dielectric barrier.
Yet another aspect of the present invention relates to a method of removing odorous compounds from an odorous gas. The method includes generating an ozone, mixing the odorous gas with the ozone to remove a first portion of the odorous compounds from the odorous gas, and passing the odorous gas through a non-thermal, non-uniform plasma to remove a second portion of the odorous compounds from the odorous gas.